Attorney General Eric Holder on Thursday vowed to aggressively enforce federal voting rights laws no matter what the Supreme Court decides this year about ending a controversial part of the 1965 Voting Rights Act.

Speaking to African-American leaders in New York City, Holder called the requirement that portions of 15 mostly southern states continue to gain Justice Department or federal court approval of any proposed changes in voting procedures "indispensable" and a "constitutional tool" to eradicate discriminatory voting procedures.

When the case was argued earlier this year, some conservative justices signaled that the provision, known as Section 5, may have outlived its usefulness.

"As we await the court's decision, I want to assure you that no matter the outcome, the Department of Justice will remain committed to the aggressive and appropriate enforcement of all voting and civil rights protections, including every part of the Voting Rights Act," Holder declared. Holder did not say how he would proceed if the court strikes down Section 5.

Holder spoke to the National Action Network, a reliably supportive organization he has addressed before, guided by the Rev. Al Sharpton, who also spoke to the crowd.

Holder joined the convention in marking the 45th anniversary of Martin Luther King's assassination.

"It's appropriate that we celebrate the remarkable, once-unimaginable progress that so many of us have seen even within our lifetimes." But Holder added, "This journey is far from over."

Holder also used his platform Thursday to make a strong personal appeal for the Obama administration's gun control measures, which are facing strong opposition on Capitol Hill.

Recalling his trip to Newtown, Connecticut, just days after the massacre at Sandy Hook Elementary School, Holder spoke of his reaction to a meeting of first responders and crime scene search officers.

"When these brave men and women asked me, with broken hearts and tear-streamed faces, to do whatever I could to prevent such a thing from happening again, I told them I would not rest until we had secured the common sense changes that they and those 26 angels deserved," Holder told the audience.